It is a well-known phenomenon that a transition metal grows in an island shape when it is deposited on the surface of a single-crystal oxide (Vollmer-Weber mode).
Japanese Patent Laid-Open No. 62-87820 discloses, as a sample for infrared absorption analysis, what is deposited Pt (platinum) as a first thin film partially transmitting infrared beams is deposited on one low-index surface of a single-crystal silicon substrate, and then a second thin film to be the sample is deposited on the first thin film (Pt).
This sample for infrared absorption analysis has an enhanced reliability of information such as molecular orientation by making the thickness of the first thin film (Pt) to a thickness partially transmitting infrared beams so that the same sample can be used for both measurement methods of the transmission method and the reflection method.
In the description, as specific thickness of the above-described first thin film (Pt), a thickness of 50 to 200 angstroms is described, and in the example, a thin Pt film of 100 angstroms is formed.
As described above, when a transition metal such as Pt is deposited on the surface of a single-crystal oxide, Pt is first deposited in an island shape on the single-crystal oxide (hereafter, this deposit is referred to as cluster), and the cluster is gradually densified to be a continuous film (thin film).
Since a Pt cluster is an aggregation of Pt atoms, and has a diameter of about 30 nm (300 angstroms) and a thickness of 6 to 8 nm (60 to 80 angstroms), films thinner than this cannot be formed. The description of the above-described patent also supports this fact.